sql-server - 查询单个表并合并相同日期时间的结果

Question

我有一个表，我在其中插入与 id 相关的值，这些值会随着时间而变化。

例子：

| 身份证 | 时间戳 | 价值 |
| 1 | 2018-09-12 02:29:31.154 | 7.139 |
| 1 | 2018-09-12 02:40:46.724 | 7.254 |
| 2 | 2018-09-06 02:40:46.724 | 132.451 |
| 1 | 2018-09-12 02:42:19.841 | 7.645 |
| 3 | 2018-09-12 03:01:45.811 | 45.276 |
| 1 | 2018-09-12 03:12:59.121 | 7.421 |
| 2 | 2018-09-12 03:12:59.121 | 130.789 |
| 1 | 2018-09-12 03:15:33.467 | 7.121 |
| 2 | 2018-09-12 03:15:33.467 | 136.198 |
| 3 | 2018-09-12 03:15:33.467 | 46.971 |
| 2 | 2018-09-12 03:27:13.642 | 131.879 |
| 3 | 2018-09-12 03:27:13.642 | 44.645 |
| 1 | 2018-09-12 03:30:27.564 | 7.691 |
| ... | ... | ... |

我的目标是进行单个查询以获取Id1、2 和 3 的日期范围之间的值并将它们合并在一起。

结果将是这样的：

{ Timestamp: "2018-09-12 02:29:31.154", id1: 7.123, id2: null, id3: null }
{ Timestamp: "2018-09-12 02:40:46.724", id1: 7.254, id2: 132.451, id3: null }
{ Timestamp: "2018-09-12 02:42:19.841", id1: 7.645, id2: null, id3: null }
{ Timestamp: "2018-09-12 03:01:45.811", id1: null, id2: null, id3: 45.276 }
{ Timestamp: "2018-09-12 03:12:59.121", id1: 7.421, id2: 130.789, id3: null }
{ Timestamp: "2018-09-12 03:15:33.467", id1: 7.121, id2: 136.198, id3: 46.971 }
{ Timestamp: "2018-09-12 03:27:13.642", id1: null, id2: 131.879, id3: 44.645 }
{ Timestamp: "2018-09-12 03:30:27.564", id1: 7.691, id2: null, id3: null }

是否可以在单个查询中进行？

标签： sql-serverlinqtsqlmerge

Answer 1

var ids = new List<int> { 1, 2, 3};

var result = (from item in db.Table
              where ids.Contains(item.id) && item.Timestamp > fromDate && item.Timestamp < toDate
              group item by item.Timestamp into sub
              select new 
              {
                  Timestamp = sub.Key,
                  id1 = sub.Where(x => x.id == 1).Select(x => x.Value).FirstOrDefault(),
                  id2 = sub.Where(x => x.id == 2).Select(x => x.Value).FirstOrDefault(),
                  id3 = sub.Where(x => x.id == 3).Select(x => x.Value).FirstOrDefault()
              }).ToList();